You are right to be nervous. Auto fires are nothing to dance around with. Unfortunately there is no way to diagnose a problem like this over the inter web. You need to start at the power source(battery) and run the circuits from there. Making sure all connections are solid and power is flowing through all components, in and out. First step would be to get a good color coded wiring diagram. Then take pics and make notes as you go through the system till you get things worked out. No shortcuts!